It seems those pages has something in that PIX is filtering. My recomendation is to resolve the name of the site to obtaing the real ip address then read the LOGs from the PIX. Filter out temporaly several not important LOG messages to get focuce. To do this use following commands:

conf term

no logging message 109001

no logging message 109023

no logging message 113004

no logging message 210007

no logging message 302013

no logging message 302014

no logging message 302015

no logging message 302016

no logging message 302020

no logging message 302021

no logging message 304001

no logging message 305011

no logging message 305012

no logging message 609001

no logging message 609002

no logging message 710005

logg on

logg console 7

logg monitor 7

exit

On the other hand you could use the command "debug packet inside src a.b.c.d" and "debug packet outside dst x.y.z.n" to monitor the traffic flowing thru the PIX.

These tips will give at least some idea of what is going on and if the traffic is been filter for the PIX.

In the end I resolved the problem by upgrading from 7.0 to 7.2.(2). After I did this I still had the same problem however the logs showed dropped packets on the outside interface from the web server. They were dropped due to MSS Exceeded.